This invention relates to a heat exchanging wall used for causing acidic or alkaline fluids, fluids containing salts, fluids of organic compounds, etc. to undergo heat exchange with fluids of the same or different type, such heat exchanging wall having particular utility for use in heat exchangers for chemical plants and other facilities.
Heretofore, a number of methods have been used in heat exchangers for chemical plants and other facilities for preventing corrosion of the heat exchangers. In one method, the heat exchanging wall (heat transfer tubing) is made of a metal which is resistant to corrosion by a fluid that flows through the tubing. In another method, the surface of the wall made of a metal which is not resistant to corrosion by the fluid is coated with a layer of metallic material or plastics which is highly resistant to corrosion by the fluid. In a further method, graphite of high corrosion-resistance is selected as a material for the heat transfer tubing.
Some disadvantages are associated with the aforementioned methods of the prior art. Coating of the wall surface with a metallic material of high corrosion-resistance increases cost for production of the heat exchanging wall. Moreoever, when a coat of metallic material is applied to the wall surface, there are such defects as the development of a lack of continuation or openings and crack formation. Meanwhile, when a coat of plastics is applied, the problem of peeling off, swelling or cracking of the coat is encountered. Such being the case, coating of the wall surface with a metallic or plastic material does not provide a completely reliable solution to the problems of corrosion of the heat exchanging wall. Furthermore, when graphite is used as material for the heat exchanging wall, difficulty is experienced in improving the heat exchanging (heat transfer) efficiency by forming elevated and depressed areas of a complex pattern on the wall surface due to low mechanical strength of the metal.